Sportster 1800 on plane with 1 engine?

[swill777]

So here is the deal.. I completely blew out my port side pump, and bought this 95 XP pump on ebay a while back: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=150308172887

I bolted on my prop, then bolted the pump on. Boat runs great. Here is my question... The wear rings are good in both pumps, and the impellers are about the same. The new impeller housing is metal, the old stock (starboard) one is plastic.

So, using the new port-side metal 95XP pump alone, I can get my boat on plane with just me in it, and hit about 30mph.

Using the starboard side plastic OEM pump alone, I cannot get on plane. With both pumps together I hit in the high 40's GPS speed. Is this normal?? Meaning is it normal that the OEM pump can't get the boat on plane? It seems the 95XP pump is more efficient. Both motors hit 7000rpm and run the same.

It does sound like the plastic pump side is cavitating a bit, it makes a different sound on full-throttle takeoff then the metal one... but, both pumps have a new foam seal, and the shoe looks fine on both sides... ? ? ? I am almost thinking of taking a video of it for you guys to check out... Both engines going the boat runs good.. It's almost making think to just buy the same used 95XP pump to have them "matched" if it pops up on ebay.

Any thoughts? I have the 1998 sportster 1800 with the twin 717's, 85HP a side.

 

[Gunsrunner]

My challenger will not plain on either motor by it's self.
Be careful that speed without the other engine running, you can get water in the block because there is no exhaust pressure.
You are supposed to have the cooling water lines blocked off to travel on one motor!!:cheers:

 

[swill777]

Both motors were running when I did it.. the starboard motor was idling while I ran the port motor at 6-7k RPM. I don't think it will flood like that. So it sounds like my situation is "normal" and maybe it only planes on the port motor since it's a different model pump, with the same model impeller. Oh well, the boat runs great with both motors floored.

 

[scooper77515]

There will be a difference in size between your two pumps on a two-engine boat anyway. Not sure which is bigger, but one is a little bigger, from what I hear. One is supposed to be a little bigger to compensate for some force that causes the boat to want to pull to one direction, so they put a bigger pump on the other side to even it out.

 

[swill777]

Its funny, it runs pretty damn straight with both throttle set even... It's working, I'm happy, I'll have it down in the Keys in 9days... F-in A!

 

[scooper77515]

They are made to run straight when the throttles are even. One will push a little harder to overcome the steering "pull". If working correctly, you will not even know it is working.

But if not working correctly, your boat will pull like a car out of allignment.

Even my single engine boat pulls to the (left, I think, haven't driven it in forever, it seems). It is really easy to make sharp turns the other direction, but you have to pull on the steering wheel harder to turn into the pull.